1. Field of the Invention
The present invention relates to a magnetic tape where a servo signal is written on a servo band and a manufacturing method thereof, and a servo writer and servo write method for writing the servo signal on the magnetic tape.
2. Description of the Related Art
These years, in a magnetic tape for use in a backup of a computer and the like a high density recording progresses more and more, and in the future the high density recording till around several tens of terabytes is foreseen. Based upon the high density recording, in the magnetic tape a number of data tracks increases, and a width of the data tracks and a distance between adjacent data tracks become narrower. In addition, based upon an augmentation of a memory capacity, the magnetic tape itself becomes a thin layer. Furthermore, in order to handle the increase of the data tracks in the magnetic tape, in a magnetic tape recording/reproducing apparatus a number of a winding/rewinding of the magnetic tape for recording/reproducing data increases, and widths of a data signal recording/reproducing element and a servo read element also become narrower. Consequently, in order to precisely read data recorded in high density on a plurality of data tracks arranged in a lateral direction of the magnetic tape, it is necessary to accurately grasp which data track a magnetic head utilizes and performs recording/reproducing. Therefore, it becomes very important to specify which servo band out of a plurality of servo bands provided in the lateral direction of the magnetic tape a read head or a recording head refers to and is positioned at.
Conventionally, as a system for performing position control of a magnetic head by a servo signal, there are an amplitude servo method of performing the position control by a width of a read servo pattern, a timing-based servo method of performing the position control by a timing of the read servo pattern, and the like. In a system for recording the servo signal (servo pattern) of the timing-based servo method on the magnetic tape, a phase difference is provided for the servo signal of each servo band by off-setting the servo pattern of each servo band in longitudinal directions of the magnetic tape. And it is proposed to specify each servo band and identify a position of a lateral direction of a relevant data band on the magnetic tape by simultaneously reading servo signals of two servo bands at both sides for sandwiching a data track, and measuring the phase difference (for example, see Japanese paraphrase 27 and FIG. 6 in Japanese Patent Laid-Open Publication Hei 11-273040).
However, when in the method for specifying each servo band by respectively reading servo signals from two servo bands adjacent to both sides of a data band, in a recording/reproducing apparatus, not to mention both sides, a one-side servo read head for reading a servo band causes a read fault of the servo signals due to an unknown reason or a malfunction, a position of a data track in a lateral direction of the magnetic tape could become unidentificable. In addition, since it is necessary to identify and specify the data track by comparing the servo signals written on the servo bands at both sides of the data track, it could take time to access each data track.
Consequently, by reading servo a signal written on a servo band out of a plurality of servo bands are strongly requested a magnetic tape that can identify and specify a position of a data track in a lateral direction of the magnetic tape and a manufacturing method thereof, and a servo writer and servo write method that can write the servo signal on the magnetic tape.